When creating a new Group, only allow the Group creator to continue the Group creation process.

If the logged in user ID does not match the Group creator user ID, redirect back to the root group creation screen. Doing this has the added effect of resetting group creation cookies. Props Pietro Oliva. (trunk)

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7788 cdf35c40-ae34-48e0-9cc9-0c9da1808c22